1. Field of the Invention
This disclosure relates to electronic circuits, and, more particularly, to systems and methods for a digital-to-charge converter (“DQC”).
2. Description of the Related Art
A digital-to-analog converter (“DAC”) is a circuit that converts a digital signal into an analog signal. Typically, the resulting analog signal is directly proportional to the value of the digital signal. For example, the input signal may be a digital sequence of numbers provided by a controller at discrete time intervals, and the analog signal may be an analog voltage or current. Because a conventional DAC is always on, it does not work well in low-power applications. Therefore, in those situations, a DAC may be replaced with a Pulse Width Modulator (“PWM”) circuit.
In a PWM circuit, a pulse train is output with varying duty cycles as a function of a digital input signal. The pulse train is driven into an R-C low-pass filter to remove a fundamental PWM frequency, which toggles at a fixed rate that is much faster than the slew rate of the desired analog output. In the R-C low-pass filter stage, the charge in the capacitor alternates between charging and discharging while power is constantly dissipated across the resistor. When providing a digital input code to a PWM circuit, a low-power controller toggles the voltage during its active state and may be “asleep” in between the toggle times of the PWM waveform. Accordingly, the low-power controller normally “wakes up” at twice the PWM frequency, also consuming significant amounts of power.